Rats, mice and hamsters have been exposed by inhalation to arsine gas. The collaboration of many different groups within the DTRT has made it possible to investigate a variety of toxicological endpoints including histological, reproductive, hematological, immunological, and biosynthetic effects. Pilot exposures to methylene chloride have been completed and a two-year chronic exposure is in progress as part of a study being conducted in collaboration with several other groups within the NIEHS. This study is designed to investigate cellular and molecular processes responsible for the induction of lung and liver tumors and to measure changes in pharmacokinetic parameters with age and treatment. The ability to accurately control and document the exposure environment continues to be enhanced by refinements in methods of data acquisition and management. A system has been designed and implemented to manage the acquisition of data from in- life observations, weighings, and necropsies. This data combined with the environmental documentation provides a readily accessible history for each animal in a study. Work is continuing on the detailed design of a new inhalation facility. The floor plan has been completed. The design of special services, such as furnishings, containment enclosures, and air handling, control, and filtration equipment is in progress.